Cell Phone Lifetimes A recent study of the lifetimes of cell phones found the average is

24.3

months. The standard deviation is

2.6

months. If a company provides its

32

employees with a cell phone, find the probability that the mean lifetime of these phones will be less than

23.9

months. Assume cell phone life is a normally distributed variable, the sample is taken from a large population and the correction factor can be ignored. Round the final answer to at least four decimal places and intermediate

z

-value calculations to two decimal places.

P<X23.9=?